Hi Ed, I attach an expired eBay auction image that shows the machine's complete code from the left side. Another similar photo showing the right side and full v.-kenn. was posted on the LRG site. Cheers, David

Hi, Ed
KG 26 did not have five grupes.
The fourth grupe sometimes use "F" and sometimes use "E".
The fifth grupe sometimes use "F" and sometimes "G"
This plane was He 111 H-6 (WNr 4217) from Gruppenstab IV./KG 26 like several others .
Eduardo

eduardo : Yes, Stab.V/KG 25 did exist, eventually (1944)!
I have seen that in records, and it had F (1945).

However there are two versions of code letters out, the other:

The New Luftwaffe Unit Codes

These appear first in March 1939 but were finalized in an order 04.07.1939. The new unit code system was simpler than the old (but had more letters than often reported). It was as follows: The first two letters denoted Geschwader, Gruppe, Staffel or independent unit, the third was individual machine letter (and regularily painted in Staffel or Stab. colour). The fourth denoted basically Stab. or Staffel. The six Stab. indentification letters were (basically):

Other sources state the letter “F” was for V Gruppen as Stabstaffel/KG 26 was known as V/KG 26 before!
Often the fourth letter was painted Black (1H+BF) where the individual letter (here B) was Bright-Green. Late in the war the fourth letter was often used as an special single-Staffeln designator. In this example the unit (KG 26) was apparently using an Stabstaffel of eight Ju 88 A-4 (Radar-equipped) ex-Bombers for Long-Range Reconnaissence or Long-Range Radio homing from October 1944 to May 1945. Others code letters (such as A3+AE) were used as Training codes for KG 200 (the Special Secret Unit) and use of “E” is also known in other instances.

If an fourth or fifth Staffeln was added to any Gruppe the colour was Blue and Black respectively. Known use of 16. and 17. Staffel was with KG 40 (Heinkel He 177) but there may have been others. In the early years of the war the Staffel letter U was used for the Training Staffel or Kette (four aircraft) and in some rare cases the fourth letter was omitted altogether.

I am not saying that, just the system suggest that, but I am not expert on units He 111´s. However F is kind of strange, can this be 1H+BP (II Gruppen); also I do not find this aircraft in Tunis CEA lists. But thats no proof either.